The Maron theory of polymer solutions was used to reexamine the data of Brown et al. and Allen et al. [1,2] on the vapor pressures of polypropylene solutions in diisopropyl and diethyl ketones. The results obtained show that the interaction parameters for these systems depend on concentration and temperature, and that these parameters are able to reproduce the observed data so long as the polymers are amorphous. However, in the presence of polymer order, deviations from theory are observed which lead to 31 and 61% crystallinity for the two polypropylene samples used in these studies.